One day before Martha Stewart is slated to enter prison, lawyers for the multimillionaire businesswoman continued to press her appeal, accusing the government of withholding material that might have led to her acquittal.

In a letter to prosecutors and the trial judge, Stewart's attorney Walter E. Dellinger III demanded that U.S. Attorney David N. Kelley's office turn over to the defense documents related to the ink analysis of a key piece of government evidence.

Under federal law, prosecutors must turn over to the defense before trial any evidence that could seriously weaken their case, and Dellinger wrote Thursday that the recent perjury trial of Secret Service ink expert Larry F. Stewart showed that Kelley's team "has not satisfied its obligations."

Larry Stewart was acquitted earlier this week of lying on the stand during the trial of Martha Stewart, no relation, and her former broker Peter E. Bacanovic. They were convicted in March of conspiracy, obstruction and lying to federal investigators about her sale of ImClone Systems Inc. stock. Prosecutors contended that Bacanovic improperly had his assistant tip Martha Stewart that ImClone's founder was selling his stock, while the broker and his client said they had previously arranged to sell if the price fell below $60.

Bacanovic remains free on bond pending appeal, but Martha Stewart asked to begin serving her five-month prison sentence and is due to report to the federal prison camp in Alderson, W.Va., by 2 p.m. Friday.

Prosecutors charged Larry Stewart with overstating his role in testing a worksheet that Bacanovic claimed documented the $60 arrangement, so much of the testimony at his trial focused on the testing of that document.

Dellinger complained in the 10-page letter that some of the evidence that emerged during the ink expert's trial "would have supported a defense that [the Secret Service lab] sabotaged the testing . . . to give the FBI the result it wanted. That could have led to an acquittal."

Stewart's lawyers have said all along that they intend to make the prosecution's handling of the ink testing an important part of their appeal, and the letter suggests that the ink expert's acquittal has done nothing to change that strategy. "The existence of reasonable doubt in October 2004 [in Larry Stewart's trial] says nothing about the nature of the Government's misconduct in January-February 2004," Dellinger wrote.

A spokeswoman for Kelley said his office, which prosecuted both Martha Stewart and Larry Stewart, had no comment on the letter.

Martha Stewart is set to go to prison in Alderson, W.Va., today as her attorneys continue to appeal.